How to shock or disinfect a sand point or driven point well.

This article series explains how to shock a well, when, why, and exactly how to chlorinate a drinking water well. Page top illustration of a driven point well from Wisconsin DNR cited in detail at the end of this article.

How to Shock or Chlorinate a Driven Point or Sand Point Well

Because driven point or sand point wells are usually constructed using a small diameter pipe and well point mechanically driven into sandy soil we can have trouble installing the bleach solution needed to disinfect or shock the well.

This article series includes adapted information from the New York Dutchess County Health Department's environmental laboratory, along with other expert sources and with annotations, expansion & annotation. You will find this well shock procedure advice consistent with the well shocking or well chlorination procedures recommended by most health authorities.

[Click to enlarge any image]

The purpose of shock disinfection of a well system is to destroy bacterial contamination present in the well system at the time of disinfection and is not intended to kill bacteria that might be introduced at a later time.

Question: What's the best way to shock a 2" driven sandpoint well?

2019/07/18 Hunter said:

What an awesome resource this is, really glad I found it. I have a question about the new water source I put in at our cabin here in Alaska. I did a sandpoint using 2" galvanized pipe and hit water at roughly 16 feet, went down to about 25 feet and stopped there.

I hooked up a short water line to it with a check valve in between the pump and pipe. I've got water about 8 feet in the pipe leaving 17 feet free of water.

I had it tested and it came back positive for total coliform but negative for arsenic and 1.1 for nitrates which is well within limits.

I did a well shock to it but it sounds like I didn't leave it in long enough (2 hours), had it retested with the same result.

These tests are expensive but i'd like to try this one more time, any suggestions on how I should shock this particular type of well? Thanks. Hunter

This Q&A were posted originally at WELL CHLORINATION & DISINFECTION

Reply: How to shock a sand point well

Hunter

Unlike a well casing or other larger diameter wells, shocking a driven point well is more difficult as just pouring a bit of bleach into the rather small diameter well pipe doesn't assure us that it mixes throughout the well pipe's entire height. So we need to go to a bit more trouble. I'll give a suggestion below.

Key points in successful well shocking:

1. sufficient concentration of bleach - depends on volume of water being shocked, hence the table above

2. sufficient exposure time - 8-24 hours

3. assurance that bleach is thoroughly mixed in the standing well pipe or casing

You can shock those 8 ft. of water or an entire well pipe filled with water if that's how you get the bleach into the driven point well, but it's very difficult to get the bleach out into the surrounding soil. Even trying reverse pumping, using pressure to try to force bleach out into the surrounding sand isn't going to fix a source contamination issue as that contamination may in effect be infinite.

In sum, unless your shock procedure was weak, too short on exposure time, or not mixed, I don't think the problem is a well shock procedure limit - unless you put down quite contaminated piping materials.

Instead I suspect that because the water source is close to the surface the source water itself is carrying bacteria - which is entirely common in surface waters. T-coli doesn't mean septic bacteria (E-coli) but both could be present, so on your next test be sure to also test for E-coliform.

How Much Household Bleach Do We Need in a SandPoint Well?

To try shocking one more time let's calculate the volume of household bleach needed:

Assuming you're pouring bleach into the top of the driven pipe just above ground and that we want to fill the pipe so that its entire interior is disinfected let's calculate the water volume in the pipe and the volume of bleach needed.

Calculate the well pipe volume

See WELL DYNAMIC HEAD & STATIC HEAD DEFINITION - table of well water volumes per foot or per meter of depth, for examples of pipe volumes for other sizes of well pipe or well casings.

• 8ft of pipe with water +17 dry vertical well pipe = 25 ft. of 2" ID vertical pipe that may be full of water during the sanitizing procedure.
• 25' of 2" pipe is about 950 cu .in. (1 cubic inch = 0.00433 gallons)
  
  or 4.11 gallons assuming that in your shock procedure you fill the standing well pipe entirely with bleach solution so as to disinfect the whole thing.

Calculate the volume of bleach

Now from our well shocking chlorine bleach quantity table above we'd use 3 cups bleach in a 100' 6" casing - that's 3 cups for 150 gallons of water.

3c/150g = x c/ 5 g(gallons for a generous estimate for your well) - solving for x:

(3/150) x 5 = x

x = (.02cups) x 5 = 0.1 or

• 1/10 cup of household bleach for 25' of 2" ID pipe or 0.10 x 8 oz./cup = 0.8 oz of bleach
  

You could use one ounce of household bleach or at most 2 ounces. More is OK but don't use straight bleach or you'll have a devil of a time flushing out the well.

Key Steps to Successful Sandpoint Well Chlorination

So as long as you've got a strong-enough concentration of water

AND
you think you mixed the bleach into the water (maybe pumping it via a small diameter hose or tube to the bottom of the well or re-circulating bleach-water solution through the standing pipe until it's mixed)

AND
you leave the bleach for sufficient time: 8-24 hours

THEN
you can flush out the well, wait a few days, flush the well a few times, then test again.

Use a Pony Pump & Tubing to Mix Driven Point Well Chlorine Solution

For effective mixing of the bleach solution in the sand point (driven point) well, a plumber typically uses a pony pump and sections of garden hose or tubing and a bucket of bleach-water solution. Connect a tee to the top of the well pipe.

Insert your tubing (clean new plastic, 1/2" is ok) down to the well bottom through one side of the tee; seal the tee opening around the entered tubing;

Connect a return pipe from the other side of the tee to your bucket.

Pump water down the tubing to the well bottom; as that water pushes well water up the pipe from the bottom it's also mixing in the bleach solution; the mixed solution flows into the bucket where the pony pump picks it up and sends it back down the tee.

Pump long enough that your return water smells like bleach and you're thus confident you've mixed the bleach solution throughout the height of the well pipe.

Follow-up:

Let me know the result.

If you still find bacteria I'd put in at least a disinfection system. (What else you might need to treat depends on what else you find in the water - ask the local water test lab if there are other common surface water contaminants found in wells in your area and thus for which you should test. )

Let me know what you try and what are the results; I'd like to see a photo of the well head and of your pump, bucket, tee, tubing setup too.

Sand Point Well Shock Procedure

It's possible to get chlorine into the well by sending it through the building piping and pump but that step won't sterilize the interior and sides of the sandpoint well casing.

• How much bleach to use when shocking a well: 1/2 oz household bleach per gallon of water treatment solution in the well or pipes
  
  Your local health department officials can give more precise guidance about the amount of disinfectant needed based on the depth of the well.
  
  For a separate well disinfection quantity table for difficult cases such as well & equipment disinfection after area flooding see WELL DISINFECTANT TABLE, POST FLOODING.

Notes to the table above

1. How Much Bleach to Use per Gallon of Water: Checking the math:

Typical recommended chlorine concentration to shock a well is 3 pints (6 cups or 48 fluid ounces) of household bleach for every 100 gallons of water in the system (or in the well if you're only treating the well itself).

That calculates to 0.48 oz / gallon or about 1/2 ounce per gallon.

Other health sources recommend 1 ½ ounces of bleach per each 10 gallons of water volume in pipes or tanks being sanitized.

That calculates to 0.15 ounces per gallon - so you can see that there is a wide range of "opinion". In OUR opinion it's safer to use a stronger bleach solution but don't overdo it or you'll have trouble flushing the bleach from the well.

A reasonable concentration (assuming an 8-24 hour exposure or wait time) is 1/10 to 2/10 ounces of bleach per gallon.

Using a standard of 3 US Cups of Bleach / 100' of 6" well casing = 0.02 cups per foot where 1 foot of 6" casing is about 1.5 gallons, so 0.02 Cups / 1.5 gallons, or 0.013 cups/gallon - that's a concentration of (0.013cups x 8 oz/cup) or

• 0.1 liquid ounce of bleach per gallon of water or 1 ounce of bleach for every 10 gallons of water to be made into a well disinfectant solution.
• 1-inch pipe volume: 9.4 cu.in of water per Foot or 0.04 gallons per ft. or 0.32 liquid oz. per ft.
• 2-inch pipe volume: 37.7 cu .in. of water per Foot or 0.16 gallons per ft. or 1.28 liquid oz per ft.
• 1 US Liquid Gallon = 231 cubic inches

For a table of volumes of water in wells or pipes of various diameters

see WELL DYNAMIC HEAD & STATIC HEAD DEFINITION

Watch out:The pH of the water affects the amount of disinfectant bleach needed.

See details at WELL DISINFECTANT pH ADJUSTMENT

2. Treat the water not the air:

Watch out: NOTE to be accurate in reaching the necessary concentration of chlorine in your well, treat the "depths" listed above as if they were the height of the actual column of water in your well (assuming a standard casing which is 1.5 gallons per foot of height).

So if your well is 400 feet deep, but if 100 feet of it is air, your water depth is actually 300 ft. The actual quantity of water in a well bore when the well is at rest is defined as the static head.

Actual well water volume: See WELL DYNAMIC HEAD & STATIC HEAD DEFINITION for a table of well water volumes per foot or per meter of depth.

3. Other warnings for well shockers

Choices of well disinfectants are detailed at WELL DISINFECTANT CHOICES

More about how to measure the actual depth of a well is at DEPTH of a WELL, HOW TO MEASURE.

Watch out: don't forget to flush first then sanitize everything: all of the well piping, pumps, tanks, in the system. Remember to drain water tanks and pressure tanks of bleach solution when flushing the disinfectant after the wait period.

Watch out: for inadequate well disinfection: use enough bleach to reach the necessary concentration in the well and let the disinfectant remain in the well long enough (8-24 hours) - otherwise you may fail to adequately disinfect the well.

Watch out: for excessive well disinfection: don't significantly "overdose" the well with bleach or chlorine or you may find that you have to waste a lot of water and time flushing out the chlorine bleach at the end of the disinfection period.

Watch out: for difficult-to-sanitize wells or if the water well has been contaminated by area flooding extra steps and extra safety precautions needed.

Details are at WELL DISINFECTION after a FLOOD

If you need to disinfect in-building water equipment such as a water tank or water heater or water softener,

see WATER TREATMENT EQUIPMENT DISINFECTION

Well Sanitizing References

• ADOE, Water Well Management Level 2 Training Module. Prairie Farm Rehabilitation Administration of Agriculture and Agri-Food Canada, Alberta Environment, Alberta Water Well Drilling Association and Alberta Agriculture, Food and Rural Development
• ADOE, Water Wells that last for Generations. Alberta Agriculture, Food and Rural Development; Alberta Environment; Prairie Farm Rehabilitation Administration of Agriculture and Agri-Food Canada
• AWDA, Water Well Management Level 2 Training Module. Prairie Farm Rehabilitation Administration of Agriculture and Agri-Food Canada, Alberta Environment, Alberta Water Well Drilling Association and Alberta Agriculture, Food and Rural Development
• ATSDR Agency for Toxic Substances Disease Registry, Toxic Substances Portal: CHLORINE TOXICITY, [PDF] November 2010, retrieved 8/27/2013, original source: www.atsdr.cdc.gov
• Canadian BC Ministry of Environment, "Water Stewardship Information Series: WHEN STANDARD WATER WELL CHLORINATION PROCEDURES are INEFFECTIVE [PDF] Fact Sheet developed for Well Drillers, Health Authority Staff and others involved in well recovery efforts after a flood [PDF] Agriculture and Agri-Food, Canada, retrieved 4/8/2013 original source: http://www.env.gov.bc.ca/wsd/plan_protect_sustain/ groundwater/wells/factsheets/PFRA_well_recovery.pdf
• DRIVEN POINT (Sand-Point) WELLS, [PDF] Wisconsin Department of Natural Resources, PUB DG 022 2010 retrieved 2018/06/12, original source: https://dnr.wi.gov/files/PDF/pubs/DG/DG0022.pdf
• Mancl, Karen, "Bacteria in Drinking Water" - "Chlorine," Karen Mancl, water quality specialist, Agricultural Engineering, Ohio State University Extension. Mancl explains factors affecting the effectiveness of chlorine in water as a means to destroy bacteria and other microorganisms. OSU reports as follows:

  Chlorine kills bacteria, including disease-causing organisms and the nuisance organism, iron bacteria.
  
  However, low levels of chlorine, normally used to disinfect water, are not an effective treatment for giardia cysts.
  
  A chlorine level of over 10 mg/L [1.3353e-6 ounces of bleach per US gallon ? sic. Ed.] must be maintained for at least 30 minutes to kill giardia cysts. -- http://ohioline.osu.edu/b795/index.html is the front page of this bulletin.

• Saha, Uttam, Leticia Sonon, Pamela Turner, David Kissel, Jourge Atiles, Paul Vendrell, DISINFECTING YOUR WELL WATER: SHOCK CHLORINATION [PDF] University of Georgia Cooperative Extension, retrieved 2019/07/18 original source: http://aesl.ces.uga.edu/publications/watercirc/ShockChlorination.pdf
• Schnieders, John,m Chemical Cleaning, Disinfection and Decontamination of Water Wells. . Published by Johnson Screens Inc. St. Paul, MN
• U. Nebraska, “Shock Chlorination of Domestic Water Supplies,” Cooperative Extension Service, University of Nebraska-Lincoln.
• U. Georgia, “Shock Chlorination of Home Wells, Springs and Cisterns,” University of Georgia Cooperative Extension
• US EPA, CHLORINE DIOXIDE (Alternative Water Disinfectants Manual) [PDF] U.S. Environmental Protection Agency
• US EPA, "Water: Basic Information about Regulated Drinking Water Contaminants", retrieved 8/27/2013, original source http://water.epa.gov/drink/contaminants/basicinformation/disinfectants.cfm
• US EPA, DRINKING WATER from HOUSEHOLD WELLS - PDF, U.S. EPA, Original source last retrieved 2/13/2013, original source: http://www.epa.gov/privatewells/pdfs/household_wells.pdf
• Virginia Household Water Quality Program: Shock Chlorination: Disinfecting Private Household Water Supply Systems. Virginia Cooperative Extension, Virginia Polytechnic Institute and State University.
• WDNR. 2008. Well Chlorination in Arsenic Sensitive Areas. PUB-DG-069 2002 Wisconsin Department of Natural Resources. Available online at: http://dnr.wi.gov/org/water/dwg/wellchlorination.pdf

 

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Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2019-08-13 by (mod) - follow-up tests find Coliform but not E. Coli in sandpoint well: now what?

Hunter

This is a helpful but disappointing water test result. Your lab found

Arsenic - not detected

Total Nitrate / Nitrite-N 1.11 mg/L (this is less than the allowable limit of 10 mg/L)

E.Coli - "negative" (meaning there was less than 1 CFU per 100 ml)

Total Coliform - "Positive" (this means that there was some un-specified quantity of Coliform bacteria detected in the sample, somewhere more than 100 / mL

When a lab simply gives a YES OR NO answer we lack information that would be far more diagnostic and more helpful.

That's why I wanted a bacteria count test (CFU colony forming units per 100 ml) not just a positive or negative result (which is quicker easier, cheaper, more profitable for the lab).

Consider that if the bacteria count is quite low there's a chance proper shocking will fix the trouble while if its quite high there's more likely to be a persistent contaminant source in the water supplhy and thus post-disinfection treatment is going to be necessary.

You understand that even though there's no E. coli - I.e. no sewage bacteria - detected, you don't want to be drinking the other coliform either, and as I arm-waved before, the presence of T coli also means that any other contaminant that's on the surface can be seeping into a well; good to rule out arsenic;

- ask a local water test lab what contaminants are often found in wells in your area - to see if there are other things you want to screen for

- you can also do some of the cluster or group tests such as the FHA series that are reasonable screens for common contaminants

- ultimately for drinking water you'd want at least a disinfection system on this water supply; before relying on just UV I'd want to know there's no giardia in the water as UV won't get that.

The ARTICLE INDEX lists types of water tests & options

On 2019-08-12 by Hunter

Dan, i emailed our test results to you today, hopefully that will tell you what you need to know.

On 2019-07-19 by (mod) -

Hunter, the present comments box code lets you attach one image per comment - you might want to email me the result - find our email at the CONTACT link.

Any shallow well is very likely to pick up surface contaminants - among which coliform is ubiquitous. I consider coliform found in any water test to be an indicator that surface water is entering the well and thus a warning that any contaminant on the surface that drains towards the well may be there. You're testing for the obvious ones; not much to add except asking your test lab what else they've found in wells in your area.

It was indeed a detailed response to an excellent and helpful question. I spent about a day on it if I'm candid. Working together helps us both. Your question pointed out a hole in our information; there are plenty of driven point or sandpoint wells - so probably other readers wanting the same information on sandpoint well shocking. Thanks for asking.

On 2019-07-19 by Hunter

Here are the results from our water test.

On 2019-07-19 by Hunter

Wow, I wasnt expecting such a quick and detailed response, thanks for that. As for testing the water for other contaminants, we had it tested for arsenic and nitrates and it came back with no arsenic detected and 1.1 ppm on the nitrates, with 10 ppm being the top of the acceptable scale. It also tested negative for e-Coli but positive for total coliform.

When we shocked the well last time we used quite a bit more than 2oz of bleach but we didn't let it set long enough plus we alos didn't have any water in the up 17 feet of empty pipe, we'll make sure to do that next time we shock it.

If for some reason we can;'t ge it to pass we'll just use the water for washing dishes, showers and for the toilet. I'm not sure where the bacteria is coming from if it's in the water, we are on a small ridge and there is nobody else with water on our side of it. I'll keep an eye on this page for more repsonses and will let you know what the results are of our next test.

...

Continue reading at WELL CHLORINATION & DISINFECTION - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

Recommended Articles

• DRIVEN POINT WELLS - home
• DRIVEN POINT WELL RESTORATION
• FAILED WATER TESTS - WHEN to RE-TEST
• FLOOD CONTAMINATED WELL RESTORE & PROTECT
• WELL DYNAMIC HEAD & STATIC HEAD DEFINITION - table of well water volumes per foot or per meter of depth
• WATER POLLUTANT SOURCES
• WATER QUALITY TESTS, CONTAMINANTS, TREATMENT - home
• WATER TEST INTERPRETATION
• WATER TREATMENT EQUIPMENT DISINFECTION
• WATER WELL CONTAMINATION HAZARDS
• WELL CHLORINATION & DISINFECTION
• WELL CHLORINATION DRIVEN SAND POINT
• WELL CLEANING PROCEDURES
• WELL CLEANING & RESTORATION by GLYCOLIC ACID
• WELL DISINFECTANT CHOICES
• WELL DISINFECTANT pH ADJUSTMENT

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